<!DOCTYPE html> 
<html>
   <head>标题学习</head>
   <body>
     <h1>h1 标题标签</h1>
     <h2>h2 标题标签</h2>
     <h3>h3 标题标签</h3>
     <h4>h4 标题标签</h4>
     <h5>h5 标题标签</h5>
     <h6>h6 标题标签</h6>
   </body>
</html>